Manufacture of arsenic acid



Feb. 10, 1925.

E. W. WESCOTT MANUFACTURE OF ARSENIC ACID Filed Nov. 9 19gb 31-11;: 11 foz ErrzesfiWacoi? as, m M 1 'QJEIASELA FALLS, YGRK, ASSEGIEQ'E, BY UEGXG- D-L DEVEZZASPEEEEJT CGEPURATEQH, Q12 #1:.

LAEiAUHUSETTQ, A LEQRFQTLATKGR' MASSACHUSETTS.

o n'caiiae filed iiwemberc, mac. Serial No.

To all whom it may concc m:

Be it known time i, ERNEST Wcscon, a, citizen of the Uni-teal Simbee, c siding zit Niagara Falls, in the county of iegere; and Staie of New York, have invented certain new and useful Improvements in the Mannlecture cf Arsenic Acid, cf which the following is a specification.

This invention relates to the manufacture of arsenic acid; ami it comprises a method of forming arsenic acid wherein arsenioue chlorid is treeizecl with chlcriii in the pres ence of limitecl amounie cf waiter, thereby producing e conccnire-ic seluticn of ac senic acid and vegcccs c2? Elfil more specifically, :1 method of forming arsenic acid from certain ersenid sires, wherein such are is chlorinated, usually with seine excess of cliioi'in and the efilueni; vapors wiili or without; ccnclenseticn of some ecseziicus clilcrid, are so treated with water and such further amount", 0f chlcrin {LS may be necessary; all as more fully hereinafter fo'rili and as claimed.

Arsenic amid and zirseiieies are (iesimble commercieily for 21, number of uses; among chem lieiiw" the, manufacture of insecticides. (lustomcrily, the arsenic eciil is produced by the oxicletion of ersenieue acid, or White arsenic by vzirious metiieiis of a, more 01 less complicefieii and expens cc nature, In the present invention 1 utilize another mm teriel, namely crsenicus cliloz'id, tliercby ee caring a. simpler and cheaperopemiicn and being enabled be make use of ihe lay-products of certain metallurgical pros;

Arsciiicce cliloricl is a lice-v T liq ing as, about 130 and miecible with smell amounts cf'wateiwithout mnc apparent (lecompositien. l have fcumi at i can directly oxidize it t0 arsenic acid by chlorin in the presence of water. The reaciicn evolv-EQ'mucl: beet sum ilie precinct is, or

. mey 03, c 110i; sirciig sleepy solution of e1.-

givcwiili giecper ebeorpcicc me acid (ll-l iiefiq) containing but liiile he Hill else produced. in the reaction; most cit ilie @131, under pi'cper condiiicns of em 'ei'eiien, going off as gas since it ie but iifsE-le selcble in each selizizioce oi? ic eciii, With the use cf 'chlcrizi i'eecexiebly free from Reece $51583, the HQ ecclvezl ie of cenceziieece clierecier an 'edcgiiecl to l-lCl solution, or murietic ecicl, cf the Si'ISJHle :ml 1.2 specific gravity. This acid may or senic is permissible in acid used in eerie-iii metallurgical operations. arsenic is a desidereifium the effluent vapors may be scrubbed with sii'ong'llill soliii icn in the presence 0; e little chlcrin price is condensation in towers or tourelles. The theoretical amount of Water required by the chemical reactions to furnish solid 'll i isi'l is ebcut 4 pails by weight for each 10 parts by eight of cisenioue ClllOXid; and l ordinerily employ between. 8 and 16 in making; a strong SOllEt-lfln; the exact amcunt depending, of course upon the strength of the arsenic acid solution which is clesirecl, and upon the details of the zippm'etue use&. With 10 certs by Weight of ersenious chlorid and 4 parts of Water, the amount of solid l-l fisO which can be formed is about 7.8 parts. Using 8 parts of water, the result is about a 66 per cent acid; While Vvllll'). 16 penis of Water, the result is an acid of :ioou'; 39 per cent arsenic acid.

Wliile arsenions clilorid from any source may be used in the described. process, in practice l have foimcl' it desirable anal Ed'- vzmmg cue, as Well as economical to use that produced in certain pi'ccesses of chlorineting various m'senid ores, noiably the Canadian cobiilt ores. These ci'senid ores, which are difficult of lieiieficiuiion by ordinary metallurgical mcthodsgon treeii'nent with cliloi'in gas hem? up and evolve vapors of ai-senicus clilcricl, leaving a residue of fixed metallic chloride from which the me tallic values are readily recoverable by ordie nary riiciliccis. Speissee may be treated in the same way. These vapors which i suz liy 'cai'i'y consiclemble ifi'ee chlorin, from the iisecf an excess in chlorination of the cre,

me be (liiecily ii'eaicil by the present fpmccss, thereby utiliznw l2lzlS excess of clilcrm. It is merely necessm y to mid such further amount of chlorin to iilie vapors as may lie requiretl and contact the mixture with e liiiriiieai amount of hotwebei o1','betber, with a. hot solution of arsenic acid containing the required amount. of Wafer. Or the vepoi from the chlei'inziiicn may be cooled, thereby depositing; much er most of the arecnioue Wliere ebsei icc of or portions of chlorin. it is advantageous, inl

chlorid in the liquid state, and the residual mixture of free chlorin, uncondensed arsenious chlorid and inert gases, so treated. In these gases, after condensation of some or most of the arsenious chlorid, the ratio of chlorin to arsenious chlorid is of course ihigher' than in the original gases coming from the chlorinator, and there is frequently 'no need for the addition of morc chlorin. Where the Waste gases contain large prothe present method, to so control the cooling "for the condensation of arsenious chlorid as to leave an equivalent proportion of arsenious chlorid vapors uncondensed. The possibility of utilizing the waste gases commg from the arscnious chlorid condensers is one of the advantageous features oi the present method as it obviates the necessity for scrubbing to get rid of unwndcnscd AsCl vapors. Arscnious chlorid has a substantial vapor tension at low temperatures and Where there is any substantial amount of other gases present, mere cooling will not condense it out with suil'icient thoroughness to obviate the necessity of scrubbing the elfiuent gases or vapors. In scrubbing the excess of chlorin is lost.

The water necessary in the reaction may be contained in a strong solution of arsenic acid in Water. On contacting such a solution with arsenious chlor'id and chlorin, the arsenious chlorid goes over, practically quantitatively, into arsenic acid with the liberation of HCL The arsenic acid joins that in the bath while the. Hill, being very little soluble in hot concentrated solutions of arsenic acid, passes forward in the gaseous form and may be, as stated, collected and recovered. In the presence of free chlorin the oxidation of HCl by arsenic acid, that is, the converse reaction, does not take place. By a suitable adjustment of conditions on feeding arsenious chlorid vapors and chlorin into a tower of the gcncral type of a column still or scrubbing tower and supplied with a downflow of Water, a hot strong solution of arsenic acid containing very little l lCl, arscnious chlorid or tree chlorin, can be the top a concciniratcd gaseous HCl passes forward for utilization elsewhere. Using arscnious chlorid vapors and chlorin free. from inert gases, the lCl gas is undiluted. except by water vapor and is readily cou densed. .As stated, prior to condensation, it may be given a n'iuriatio acid scrub in ihc' presence of a little chlorin this bcingaddcd if not already present) to get rid of: traces of arsenic.

In another application, lo'crial ro. 349.578. 1 have described and claimed a method ct utilizing the values of various arsenid ores rehab and the like wherein ihc o: granular-er". l in Withdrawn at the base of the tower while at countercurrent through a hot zone againsta current of chlorin gas, This chlorin may come from an electrolytic cell or may he gaseous chlorin produced from commercial liquid chlorin or may be chlorin from any source. With ores rich in arscnids, thci liberation of heat in the chlorinationreact ion is generally enough to make it self-sustaining. The vapors Withdrawn from contact with the orcs are, or may be, nearly purc arsenious chlorid; containing however of course Whatever excess of chlorin may have been used in the reaction. Ordinarily the apparatus is run under a little suction to prevent outward leakage, and in this case more or less air is apt to enter the system and dilute the vapors somewhat. \Vhcre temperatures in the chlorination are carried high enough to permit a volatiliz ation of ferric chlorld, this may also come over in the vapors and may be condensed and scparatcd for the most part by a limited degree ofprecooling. On then cooling the vapors to a low temperature, the fisCl, con- (lenses to an extent depending partly on the temperature and partly on its concentration in thea'apors. AsCl has considerable ""por tension at evcn'low temperatures and where the vapors are diluted with any amount of permanent gases (air, chlorin. etc), substantialamounts may escape condensation for this reason. It is therefore necessary to pass residual uncondenscd gases through a scrubbing tower. In the present invention this scrubbing operation may be used to produce arsenic acid. With these vapors goes forward'most oi the excess of chlorin originally used. The cooled mixture of uncondenscd vapors and gases may he, simply passed into a tower or column still through Which water is flowing in a limited amount, If not enough chlorin is already present to correspond to the arsenicrs chlorid, some'is added. The chlorin anrl' arsenious chlorid entering the tower come into contact with a strong' downllowing sol;- tlon of arsenic acid, forming 'l'rcsh urscnic acid which goes into solution, while gaseous HCl and Water vapor puss upward and on for condensation elsewhere. In the presence of chlorine, with a limited amount oi water in the system, there is substantially no lccon'lposition oi :u'scuious chlorid to Form arsenic trioxid.

My invention of course may as well be applied to the whole amount of "vapors of llU 'Urthe condensed urse'nious chlorid may he revsporized, the vapors mixed with the requisite amount of chlorin and the mixture treated in the some manner, This is particularly advantageous in the'manufacture of li'lCl formetullurgicul. muriutio ucid, since it precludes the presence of diluting inert guess and therefore allows production of strong cold. Be'voporiziug is also desirable where s particularly pure arsenic acid is desired, as it allows a, better separation of a-rseuious ohlomd from iron chlorid than is understood ways.

As justed stated, the method is carried iii u'ious chlorid, chlorin gas. and water being continuously supplied to a reaction chamber of the general type of s column.

still, while arseuio acid in strong solution is withdrawn ut the base. The process may however he carried out by what may be termed a batch method, a certain amount of orseuious chlorid and water contained in c, suitable still or reaction chamber, provided with reflux condenser, exit means, and collooting means for Hlill being? treated by the introduction otchlorio. thereinto. Part or all of chorin may he in the form of waste one from the chlorinator. The reaction developes a considerable amount of heat and the temperetures of the mixture steadily rise during-the. esrly port of the chlorination. Towards the end, uternul heat is or may desirable. it is not generally desirable to allow the temperature of the both to rise to the boiling point until the reaction is complete.

iii the arsenic acid is tohe used at the point of maoufa cture for the preparation of so id-zrrseuzi w, sow iesidusl HCl remainm the liquid iii z ucrul not disadvan- I togeous as it creadily be neutralized prior to he t A 1011 of the arsenutc. f a: some sold is prepared sale as standard comcondeuser which is cooled oxidation. The solution is allowed to reach the hoiling point, when Elli, water vapor and some arseuious chlorid up into the reiiup; condeosein Absorptiou oichloriii hy the liquid at first isso from the base of the tower can be rward in e continuous way, vup of means 12 and d scharge conduit 13 complete that little or none of it may reach the condenser, and an auxiliary chlorin inlet at the base of the latter is provided, which is so operated that the diluent HCl fifiully passing to exit carries a small amount of chlorin.

The additional chlorin thus supplied reacts with the arsenious chlor'id and water vapor in the condenser forming arsenic acid which returns as condensate to the still, and

HCl which joins the eiiiuont vapors. By this means the muxmiui'n amount of HCl 1S2 driven oil during the reaction, The solution is next concentrated by externally applied showing is a diagrammatic View in centralv verticsl section of a complete apparatus treating ore and producmg ursenlc sold,

Element 1 is a rotary cylinderof the general nature of a, rotary kiln with a stattionury housing at each end. The housing 2 at one and is provided with chlorin inlet 3 and valved or gated discharge at for the uteri chloride, while at the otherend the housing 5 carries an ore inlet conduit 6 and is provided with vapor conduit 7 leading (lOWIl to a suitable tank 8 for the condensstion offerric chlorid, this tank being maintuined at a temperature above the boiling point of orseuious ohlorid by suitable heating or cooling means. As shown, it is located in it took 8 containin oil or like temperature controlling fluid. Ferric chlorid condensing in this tank may be raked out at the flanged port 9. Conduit 10 loads to the condenser 11 provided with cooling Coudcnsed liquid m'sc'nious chlorid drops into storage tank 14, whence it may he removed through gated outlet 15, Uncondensed vu pors 51nd gases containing nrscnious-chlorid, chlorin, etc. pass forward through conduit. 16 to a diagrmnmuticully shown tower or column 17 supplied with u 'liiuited amount or' water at .18 and having" an outlet 19 for Hill, etc. Additional chlorin may be su plied at valved inlet 20 and stron srsemc acid solution removed. by trapped conduit 21. tower may be heated or cooled as the case may he by heating or cooling means. As shown, it is provided with a layer 22 of heat-insulating ,muterial. and heating ole monts 23, which may he steem pipes or resistance coils. As. the ursenio'us chlorid the tower against dos-incoming we or this ing cection to rciurn areenii'erousv raporsr When it'is so used. only part of the waiter required introdu ed at 18, some licin; introdu ed directly with the i'isi l, vapors by valved inlet I 'icam may he used in lieu o'l water at this point. lihile i hare merel shown ordinary distrihutor haliles: 27; opposite the liquid inle it is: to be under: Stood that any ot the as l. liquiddist dun ing or subdividing derives may he empioycd; and the lower may contain anv oi the usual rower pacicinge. each a? broken quartz coke, clay piales or ringu. etc. Additional chlorin may he added in thrdephlegmator.section by valved inlet 26.

Liquid arsenious chiorid in greater or less proportions may he supplied to the AS611. inlet (16) ot' the chloridiziug tower by valved cross connection 31'. .Vherc the up per section is uFed as a (lc 'ihlcgmaior with introduction of water at two points l ordinarily add only about 5 to 153 percent oi the total amount at inlet 15:; The waic'r so introduced prevents more than mere traces of chlorin or arsenic passing Forward with the HCl through it). communicate with usual apparatus (not shown) for making hydrochloric or :nuriatie acid, that is with towere or toureiien.

What 1. claim is:-

l. in the manufacture of arsenic acid, the

process which comprises reacting upon a limited amount of waler with. arsenious chlorid and free chloriu in such proportions asito produce a siren; solution of arsenic acid with liberation and removal of litl in the gaseous lorm.

in the manufacture or arsenic acid, the process which comprises: reactirug upon a lin'iited amount oi 'ater with areenious chlorid and free chlorin in such proportions as to produce a. strong solution of arsenic acid and heating Said solution to expel water and hydrochloric. acid.

The process of producing arsenic acid from aruenid ores which comprises chioi inatinc; such an ore to produce vapors of arsenious chlorid and reacting upon the arseuious chlorid with a limited amount of This outlet (19) maywat and sufficient free chlorin to produce a strong FOllltlOll of arsenic acid.

t. The process of producing arsenic acid :l'rom araenid ores which comprises chlori'iating such an ore to produce vapors 0f arscnious chlorid and reacting upon the arscnious chlorid with a limited amountof water and suilicient free chlorin to produce a strong solution of arsenic acid, and heating said solution to expel water and hydrochloric acid.

.3, in the manufacture of arsenic acloi we process which comprises passing vapors of arsenious chlorid and chlorin in counter current to a flow of water.

6. in the manufacture or arsenic acid the ])l'i)\'-( which comprises passing vapors'of ars nious chlorid and chlorin in counter current to a how of water, temperature condilions and the relative amount of waterbeing so adjusted that a hot strong solution of arwith? acid is formed.

2. in the manufacture of arsenic acid the process which comprises passing chlorine in counter current to a flow of water in the prc cnce of arsenious chloride.

in the utilization of arsenid ores the orocess which comprises chlorinating such ores in a heated state with an excess of rhlorin. cooling the el'lluent mixture of gases and vapors to condense part of the arsenious chlorid therefrom, and bringing the uncondensed gases and vapors into contact with a limited amount of water, additional chlorin being added in such amount as may be nec essary in connection with the ohlorin already present, to oxidize the residual arscnioua chlorid to arsenic acid.

9. In the utilization of arsenid ores the process which comprises chlorinating such tires in a heated state with an excess of chloriu, cooling the effluent. mixture of gases and vapors to condense part of the arsenious chlorid therefrom, and bringing the uncondeuecd gases and vapors into contact with a limited amount of Water, additional arsenious chlorid being added in such amount as may be necessary in, connection with the chlorin already present, to oxidize' he residual arsenious 'chlorid to arsenic acid.

W. In the manufacture of arsenic acid the process which comprises passing chlorine in counter current to a {low of water in the prowucu of arsenious chloride, temperature condii'ionS and the relative amount of water hcing so adijusted that a hot strongsolution of arsenic acid is formed.

in testimony whereof, I affix my signw lure.

ERNEST, W. wnsoorr. 

